How to prevent revolute joint rotation ?

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Hi!

I want to simulate a robot with 4 wheels (rotating around x axis) connected to 4 turrets (rotating around z axis). My problem is that when I send velocity commands to my wheels, each turret begins to rotate around z axis, even if I send them a position command to 0.0.

I have attempted several solutions :

• change inertia of my wheels to :

   wheel_ixx = wheel_mass * (wheel_radius**2 / 4.0 + wheel_thickness**2 / 12.0)
   wheel_iyy = wheel_mass * (wheel_radius**2 / 4.0 + wheel_thickness**2 / 12.0)
   wheel_izz = wheel_mass/2.0 * wheel_radius**2
  

• look at friction :

  • for the wheels :

    <friction>
      <ode>
        <mu>0.5</mu>
        <mu2>1.0</mu2>
        <slip1>0.0</slip1>
        <slip2>0.0</slip2>
      </ode>
    </friction>
    

  • for the turrets :

    <ode>
      <limit>
        <cfm>0.400000</cfm>
        <erp>0.800000</erp>
      </limit>
    </ode>
    

• try torque compensation : by applying through a gazebo plugin

  this->model->GetJoints()[i]->GetParent()->SetTorque(-this->model->GetJoints()[i]->LinkTorque(1));
  

But it is still not working. I through about sending an infinite torque to my turret so that no torque can be higher and make it rotate but I don't know how to do so. I am sending position commands to my turrets through the topic /joint_cmd so I send gazebo::msgs::JointCmd and I have access only to the name, velocity, position and force of the joint.

Can you help me please? :)